Northwest Africa 13790 | |||||||||||||||||||||||||||||||
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Basic information | Name: Northwest Africa 13790 This is an OFFICIAL meteorite name. Abbreviation: NWA 13790 Observed fall: No Year found: 2020 Country: (Northwest Africa) Mass: 838 g | ||||||||||||||||||||||||||||||
Classification history: |
This is 1 of 85 approved meteorites (plus 1 unapproved name) classified as Winonaite. [show all] Search for other: Primitive achondrites, Winonaites | ||||||||||||||||||||||||||||||
Comments: | Approved 28 Mar 2021 | ||||||||||||||||||||||||||||||
Writeup | Writeup from MB 110: Northwest Africa 13790 (NWA 13790) (Northwest Africa) Purchased: 2020 Nov Classification: Primitive achondrite (Winonaite) Physical characteristics: Some fragments have fusion crust. The main mass is 131.4 g. Petrography: (K. Metzler, IfP) Coarse-grained mafic rock, consisting of olivine (~45 vol%), low-Ca pyroxene (~10 vol%), Ca-rich pyroxene (~20 vol%), plagioclase (~10 vol%), Fe-Ni metal (~15 vol%), and small amounts of troilite. Olivine grains with reverse chemical zoning (Mg-rich reduction rims) occur. Metal occurs as isolated grains and as veins up to several cm in length. The rock shows a metamorphic texture with frequent 120° triple junctions at crystal boundaries and partly poikilitic intergrowths. Typical grain sizes vary between 100 and 500 µm. However, cm-sized areas of olivine and pyroxene, respectively, show identical optical orientation. Geochemistry: Mineral compositions and geochemistry: The mean olivine composition is Fa3.4±0.6 (Fa2.0-4.1; n=15); Fe/Mn (at.): 15.8. The mean low-Ca pyroxene composition is Fs4.4±0.3Wo1.9±0.2 (Fs3.9-5.0Wo1.6-2.2; n=15); Fe/Mn (at.): 12.6. The mean composition of Ca-rich pyroxene is Fs1.3±0.3Wo43.8±0.6 (Fs0.9-2.2Wo42.9-45.1; n=15); Fe/Mn (at.): 10.7. The mean feldspar composition is An20.9±0.7Or3.0±0.5 (An19.9-22.1Or2.1-3.8; n=10). Classification: Winonaite, based on the mineral chemistry and the high abundance and shape of Fe-Ni metal. | ||||||||||||||||||||||||||||||
Data from: MB110 Table 0 Line 0: |
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